We can classify numbers elevated to an exponent as positive or negative depending on whether the exponent is an odd number or an even number.
When the number we have is a negative number, and we elevate that number to an exponent that is an even number, the result will be a positive number. For example:
![(-2)^2=4](https://img.qammunity.org/2023/formulas/mathematics/college/pwr6to2h1c2w86hojcsg76qtyxkvz3uscc.png)
And when the number we have is a negative number (such as the case of -7) and we elevate that number to an exponent that is an odd number (such as the case of 2015), the result will be a negative number.
We can explain this result using smaller numbers, for example:
![(-2)^3](https://img.qammunity.org/2023/formulas/mathematics/college/lj1zv07jfbn71scjhb35x9bq6zmoo4ifx5.png)
We can express this as a multiplication of three times -2:
![(-2)^3=(-2)(-2)(-2)](https://img.qammunity.org/2023/formulas/mathematics/college/c791s1fcanvutioej2akvga4tzw28tzcry.png)
And the result will be negative:
![\begin{gathered} (-2)^3=(+4)(-2) \\ (-2)^3=-8 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/7gxompef0uoq32nj23fjdn276vbrlk869q.png)
This will always be the case when we have a negative number elevated to an odd power.
Answer: (-7)^2015 is a negative number because the exponent is an odd number.